1. Field of the Invention
The present invention relates to a construction of a root portion of a front side member, more specifically relates to a construction of a root portion of a front side member extended in a forward-and-backward direction (longitudinal direction) of a vehicle body.
2. Description of the Related Art
Conventionally, such a construction of a root portion of a front side member in a vehicle has been disclosed in Japanese Patent Application Laid-Open No. 7-165118 (1995), or is shown in FIG. 1.
In FIG. 1, a front side member 1, which extended in a forward-and-backward direction of a vehicle body, is joined to a dash panel 2 at a root portion R of the front side member 1 by spot-welding at front surface of the dash panel 2 and is extended beneath a floor panel 4, so the front side member 1 is bent downward at a first bent portion la on a forward side of the dash panel 2, and it is bent so as to be parallel with the floor panel 4 at a second bent portion 1b whose height is approximately same as that of the floor panel 4, and it is joined to a lower surface of the floor panel 4.
In the conventional construction, for example, when an input is applied to the front side member 1 along the direction from the front side to the rear side of the vehicle body at the time of a head-on collision, the front side member 1 has a tendency to be broken easily at a bent portion off-set in an up-and-down direction viewed from the front, namely, at the second bent portion 1b. When the front side member 1 is broken at the second bent portion 1b, the first bent portion 1a of the front side member 1 is turned around the second bent portion lb toward the dash panel 2, a joint portion 1c which is joined to the dash panel 2 and is a part of the front side member 1 is also turned, and thus the dash panel 2 might be deformed. In order to avoid this deformation, the second bent portion lb is stiffened so as not to be broken, or the dash-panel 2 is stiffened so as not to be deformed.
However, to stiffen the front side member 1 or the dash panel 2 possibly causes an increase in weight, and moreover a crushable zone which is effectively crushed at the time of a collision is possibly decreased, so there arises a problem such that absorption amount of impact energy cannot be increased.